Voltage input for harmonimeter, and methods of constructing and utilizing same

ABSTRACT

A portable instrument for locating and measuring harmonic distortion in a conductor. The instrument permits voltage and current harmonics to be easily read while the load is changing. Thus, the instrument may provide a great deal of insight as to the source of problem causing harmonics.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 169,407filed Mar. 17, 1988.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to apparatus for measuring and indicatingharmonic distortions in conductors, such as power lines. Moreparticularly, the present invention pertains to a portable,simple-to-use, and highly versatile instrument for quickly measuring andindicating a range of individual harmonic distortions in conductors.

2. Description of the Relevant Art

There are known devices for detecting and/or displaying harmonicdistortion in conductors. Such known devices are, for example, disclosedin U.S. Pat. Nos. 2,782,366, 3,916,296, and 3,927,281.

U.S. Pat. No. 2,782,366 discloses "oscillographic apparatus foranalyzing the performance of Amplifiers, Modulators, Detectors and thelike." The disclosed apparatus comprises a circuit including a testoscillator, a group of potentiometers, amplifiers tuned to first, secondand any other desired harmonic, a battery, and a group of oscilloscopesfor providing output displays. This known aparatus has manydisadvantages. For example, it is very bulky and difficult to use,especially in remote locations. Also, this apparatus can only be used intesting individual parts which have been disconnected/isolated fromtheir normal use, and harmonic distortion in voltage signals.

U.S. Pat. No. 3,916,296 discloses a high sensitivity/high resolutiondistortion analyzer including a parallel T-circuit bridge that is tunedby adjusting two variable elements, typically a resistor in one branchof the circuit and a capacitor in a second branch of the circuit. Thetuning is achieved by separate feed-back circuit that utilize a +45° ora -45° phas-shifted signal derived from an input voltage signal. Thisapparatus is substantially easier to use than that disclosed in patent2,782,366, but still has several problems and disadvantages associatedtherewith. For example, the apparatus is still quite inconvenient to use(especially in remote locations) because the operator is required toturn off the power to an electrical component before connecting theanalyzer thereto (resulting in expensive down time), and because theoperator is required to adjust the variable elements. Also, thedisclosed analyzer, like that disclosed in patent 2,782,366, is limitedto analyzing the harmonic distortions of a voltage signal, and does notinclude any means for selectively choosing various signal harmonics tobe measured.

U.S. Pat. No. 3,927,281 discloses an instrument for measuring harmonicdistortion in telephone transmission lines. The instrument measures theharmonic distortion introduced during telephone line transmission, andcan distinguish between the harmonic distortion introduced at the sendterminal and that introduced in the receiver terminal. The disclosedinstrument comprises a frequency phase lock circuit which generates"disturbance-free, in-phase and quadrature voltage signals of a receivedtest tone, the disturbance-free generated tones being different from thetransmitted test tone as a result of possible frequency shift along thetransmission channel and phase shifts in the terminal equipment at bothends". As disclosed, the instrument is connected to an oscilloscope forproviding an output display. This instrument has associated therewithsubstantially the same problems and disadvantages as discussed abovewith regard to the analyzer disclosed in U.S. Pat. No. 3,916,296.

Conventional distortion analyzers, including those discussed above, havemany problems and disadvantages associated therewith, and have as awhole failed to fulfill a need in the art for a portable, simple-to-useand highly versatile instrument which can be used for quickly and easilylocating and measuring problem-causing harmonic distortion insubstantially any conductor while the conductor is in normal operation.

SUMMARY OF THE INVENTION

The present invention has been designed to overcome the many problemsand disadvantages of known harmonic distortion analyzers, and to satisfya great need in the art, as discussed above.

According to the present invention, there is provided an apparatus forlocating and measuring harmonic distortion in a conductor, the apparatuscomprising a first means detachably connectable to a conductor forproviding an input signal indicative of electrical energy in theconductor, a second means connected to the first means and receiving theinput signal therefrom, the second means providing a modified signalindicative of the strength of a single, predetermined harmonic of theinput signal, and third means connected to the second to the means forselectively varying the single, predetermined harmonic which isindicated by the modified signal.

Additionally, the apparatus according to the present invention mayfurther comprise a fourth means connected to the third means andreceiving the modified signal therefrom, the fourth means providing thedisplay of the modified signal, and a fifth means interconnected betweenthe first and second means for automatically controlling a gain of theinput signal so that the input signal remains essentially constantdespite variations of the electrical energy in the conductor.

It is an object of the present invention to provide a portable,simple-to-use and highly versatile instrument for measuring a range ofindividual harmonic distortions in electrical conductors, and forreadily locating sources of such harmonic distortions.

Another object of the present invention is the provision of such aninstrument which can be readily attached to conductors, such as powerlines, while electrical energy is continuously present therein, or inother words, without circuit interruptions.

A further object of the present invention is the provision of such aninstrument capable of producing accurate harmonic measurements andindications over very large voltage and current ranges.

Still another object of the present invention is the provision of a fastacting auto-gain circuit acting on an input signal from the first meansto thereby eliminate the need for manually zeroing the instrument ascircuit loads vary, and so that harmonics can be easily and accuratelyread while the amount of electrical energy in the conductor is changing.

Yet another object of the present invention is the provision of such aninstrument which is very compactly and efficiently arranged in animpact-resistant, water-resistant case such that an operator can easilycarry and manipulate an instrument with a single hand.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,when taken into conjunction with the annexed drawings, discloses apreferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portable instrument according to thepresent invention.

FIG. 2 is a block diagram of a main circuit of the instrument shown inFIG. 1.

FIG. 3 is a block diagram of an internal, rechargeable power supply ofthe instrument shown in FIG. 1.

FIG. 4 is a schematic diagram of the main circuit for the instrument.

FIG. 5a is a schematic diagram of the power supply circuit, and FIG. 5bis a schematic diagram of a low battery indicator circuit for the powersupply.

FIG. 6 is a schematic diagram of the voltage input box.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a portable instrument according tothe preferred embodiment of the invention, which is generally indicatedby reference numeral 1. The instrument includes a carrying case 2 whichinternally houses the main circuit 4 shown in FIG. 4, the power supplycircuit 6 shown in FIG. 5a, and the lower battery indicator circuit 9shown in FIG. 5b; a clamp on current transformer 8 which is selectivelyconnectable to the main circuit 4 through a signal input jack 32; apower on/off switch 10 and a corresponding power on indicator light 12;a display scale 14 for indicating the level of harmonic distortion; aselector switch 16 which permits an operator to select a particularharmonic which is to be shown on the display scale 14; a low batteryindicator light 18; a battery charging cord 20 and a corresponding powerinput jack 22. Additionally, input jacks 130 may be included formeasuring the voltage harmonics.

The case 2 is preferably constructed from a moldable, impact-resistant,water-resistant plastic, and has the circuits 4, 6, 9 permanentlymounted in a base portion 24 thereof below a face plate 26. The powersupply circuit 6 preferably includes the pair of rechargeable batterypacks 28, 29 (FIG. 5a), which battery packs would be recharged whennecessary using the removable charging cord 20. However, circuit 6 couldhave any other appropriate/desired construction. For example, thecircuit 6 could include a single battery pack and a voltage inverter.

The current transformer 8 is selectively connectable to the main circuit4 through a signal cord 30 which plugs into the signal input jack 32 onthe face plate 26. The depicted, preferred current transformer 8 is aconventional, readily available component constructed as two halves 34,36 each including a portion of the transformer core 35 at one endthereof. The halves 34, 36 are pivotally connected together such thatthe portions of the transformer core 35 can be opened by manuallysqueezing together a pair of handles 38, 40 at opposite ends of thehalves 34, 36 thereof. The current transformer 8 also includes a biasingmeans (not shown) for normally holding the core end of the transformerin a closed position. The current transformer 8 can be easily attachedto/around substantially any conductor by simply squeezing the handles38, 40 together, positioning the opened end of the circuit transformernext to the conductor, and releasing the handles so that the opened endof the transformer clamps around the conductor. Thus, the currenttransformer can be clamped around the conductor without interrupting thecircuit, thereby enabling measurements during plant operation.

The current transformer 8 preferably has a frequency response to atleast 5 kilohertz so that higher harmonics are not attenuated and sothat the transformer provides an accurate input signal over a largemeasurement range. Also, the transformer is preferably insulated topermit measurement in bus bar systems energized up to very highvoltages, such as up to 600 volts AC.

The harmonic selector switch 16 permits an operator to choose theparticular harmonic which is to be measured by the instrument. Theselector switch is preferably constructed as a rotatable dial whichlocks into a plurality of positions corresponding to the variousharmonics. For example, in a preferred construction of the invention,the selector switch 16 could be rotated to eleven different positionscorresponding to current or voltage amplitude for the fundamental, 2ndharmonic, and odd harmonic 3rd through 19th. These harmonics are themost likely to cause problems in electrical power systems.

The display scale 14 provides output readings for the instrument, whichreadings show the amplitude of the selector harmonic as a percentage ofthe fundamental amplitude. As shown, the display scale 14 is preferablyconstructed as a multi-step light bar and a corresponding printed scalereading 0% to 100% for current harmonics or 0% to 10% for voltageharmonics.

Optionally, the instrument 1 may also include a recording device (notshown) as is well known in the art, such as a paper chart and a markingtool, which could record the output readings over a period of time.

When the instrument 1 is not being used, or is being transported, thesignal cord 30, the charging cord 20, or the plugs 128 with voltageinput box 125 and test probes 127, are disconnected from theirassociated jacks 22, 32, 130 and a lid 25 of the case 2, is secured overthe base 24 by latches 27. Also, a padded carrying case (not shown) maybe used for conveniently carrying the case 2, the current transformer 8,the voltage input box 125, the signal cord 30 and the charing cord 20during transportation or period of non-use.

Referring to FIGS. 2 and 4 there is respectively shown a block diagramand a schematic diagram of the main circuit 4 of the instrument 1. Themain circuit 4 comprises an input signal conditioner 50 which receivesan input signal from the current transformer 8, auto-gain circuit 52,which receives a conditioned input signal from the conditioner 50, abuffer 54, a filter 56 which filters the input signal and provides amodified signal indicative of the strength of a single predeterminedharmonic of the input signal (corresponding to the harmonic chosen usingthe selector switch 16) relative to the strength of the fundamentalfrequency component of the input signal, a programmable clock orfrequency synthesizer 58 which includes the harmonic selector switch 16and is connected to the filter 56 for permitting the operator toselectively vary the single, predetermined harmonic which is indicatedby the modified signal, an amplifier 60, and a display circuit 62.

According to one embodiment of the present invention the instrument 1 isused to measure a current input signal from the current transformer 8.However, it is within the scope of the present invention that theinstrument 1 could alternately be used to measure the harmonicdistortions of a voltage input signal by connecting the main circuit 4between the conductor and ground.

To measure the harmonic distortions of a voltage input, a voltage inputbox 125, (FIG. 6), containing a voltage divider network 129 to providethe proper operating voltage for the main circuit 4 of the harmonimeteris provided. The line voltage (600/480 or 240)is reduced toapproximately 33 mv which is the correct operating voltage for the 741op-amp input. As shown in FIG. 6, the input box 125 includes test probes127 and output plug 128. Output plug 128 connects to the harmonimetermain circuit 4 at connection 130 shown in FIG. 4. The switch 126 in FIG.6 is a DPDT (Double Pole/Double Throw) switch and is shown in the 240volt position. The alternate position for switch 126 is 600/480 volts.

As shown in FIG. 4, connection 130 receives plug 128. Thevoltage/current input circuit 131 connects the proper input to theamplifier input and changes the gain of the amplifier. Voltage/currentinput circuit 131 comprises a second DPDT switch 133. Switch 133 directsthe input to the proper part of the input signal conditioner (50) andenables the harmonic scale to read 0% to 10% voltage harmonics insteadof 0% to 100% of current harmonics, and vise versa. The switch 133 isshown in the "voltage harmonic" position. The alternate position wouldmeasure "current harmonics".

The input signal conditioner 50 shown in FIG. 2 is indicated as havingboth a "current to voltage" portion and a "voltage to voltage" portioncorresponding to a current input signal and a voltage input signal,respectively.

The auto-gain circuit 52 is constructed for fast-acting, state of theart electronic components which are initially factory calibrated,thereby eliminating any need for manually zeroing the meter before eachuse, or as the amount of electrical energy in the conductor varies. Thisfeature of the present invention desirably permits harmonics to beeasily read while the load is changing. Thus, data can be taken to showthe dependence of a single harmonic or several harmonics upon changingload conditions, and such data can provide a great deal of insight as tothe source of problem-causing harmonics.

The preferred embodiment of the auto-gain circuit 52 comprises a voltageto current converter (or rectifier) 64, a buffer 66, a current control,variable gain amplifier (or cell) 68 and an operational amplifier(op-amp) 70. Note, there are available compandor chips, such as NE 571which combines elements 64-70 and NE 572 which combines elements 64-68,that could be used in the present invention. The automatic gain circuit52 receives an input signal from the signal conditioner 50 and controlsthe gain of the input signal to provide a substantially constant outputsignal to the buffer 54. Rectifier 64 and op-amp 70 receive power inputfrom the battery 28 at terminal 72, 74, respectively, while op-amp 70 isalso connected to battery 29 at terminal 76. Buffer 54 is connected tobattery 29 at terminals 78, 80.

Filter 56 preferably comprises a multiple-order programmable, switchedcapacitor filter 82, such as LTC 1061 CN, and an amplifier 84. Thefilter 82 would preferably be programmed as a band pass filter usingknown software, and would be connected to battery 29 at terminals 86,88. However, the filter 56 could comprise any desired or appropriatemeans. For example, the filter 56 could be constructed as an activefilter using op-amps.

The frequency synthesizer or programmable clock 58 could, for example,comprise a source clock 90, a phase lock loop 92, a pair of "divided byn CMOS" counters 94, 96, a programmable logic array (PAL) 98, theharmonic selector switch 16, and a pull-up resistor network 100associated with the switch 16. The source clock 90 is preferably a onekilohertz source clock, such as a PXO-1000, programmed as a onekilohertz source clock, while a 4046 chip could be used as a phase lockloop 92, 4522 chips could be used as counter dividers 94, 96, and anEPROM chip, such as TMS 2516, could be used as the programmable logicarray 98. Of course, any other desired source clock 90 could be used, inwhich case a different, appropriate programmable logic array 98 mightalso have to be substituted for the TMS 2516. Components 90, 92, 94, 96,98 and 100 are each connected to the battery 29 at terminals 102, 104,106, 108, 110, and 112, respectively. The filter 56 is connected to thefrequency synthesizer 58 through the output of the phase lock loop 92.

As shown, the preferred display circuit 62 could, for example, include aplurality of LED's 114 corresponding to the number of steps in thedisplay scale 14 and at least one linear programmable chip 116, such asLM 3914, which has been appropriately programmed in a known manner.However, it will be understood that the display circuit 62 and thedisplay scale 14 could be alternatively constructed as any other desireddisplay means, such as an analog type dial meter. Also, the displayscale 14 could include multiple light bars corresponding to the numberof harmonics measured, and the main circuit 4 (including the displaycircuit 62) could be modified to provide a simultaneous display of eachof the measured harmonics as a percentage of the fundamental.

Referring to FIGS. 5a and 5b there is shown a power supply circuit 6 anda low battery indicator circuit 8 according to the present invention.The power supply circuit 6 preferably includes the pair of rechargeablebattery packs 28, 29, as discussed above, as well as a recharger circuit114 for the battery packs. The battery packs 29, 29 preferably havedifferent voltage outputs. For example, battery pack 28 could have a +12volt DC output, while battery pack 29 could have a +5 volt and a -5 voltDC output. The battery recharger circuit 114 has input terminals 116,118 which would be connectable to an appropriate power source, such as120 volts AC, through the recharger cord 20 when necessary.

The low battery indicator circuit 8 includes an amplifier 120 and a pairof LED's 122, 124, LED 122 functions as a voltage reference, while LED124 lights to indicate low battery at indicator 18. As indicated, thelow battery indicator circuit 8 is preferably connected to battery pack28 at terminal 126.

As discussed above, the main circuit 4 of the harmonic distortionmeasuring instrument 1 permits the instrument to be used formeasurements on systems having a wide range of voltages (for example, upto 600 volts), and will provide accurate harmonic readings over a verywide range of line currents (for example, over a range of 10-1000 amps).The depicted main circuit 4 could also be used to measure line currentsin the range of 0-10 amps, but such measurements would not be as usefulas measurements in the range of 10-1000 amps. It will be understood,however, that the depicted main circuit 4 is merely a preferredembodiment, and that the circuit 4 could be modified for accurate use inany voltage range and any current range.

Operation of the instrument 1 is as follows.

Initially, an operator would connect the current transformer 8 to themain circuit 4 by plugging it in to the input jack 32, and would thenclamp the current transformer 8 around a desired conductor, such as apower line. The current transformer must be connected to the input jack32 before it is clamped around the conductor, or a high voltage will bedeveloped on the transformer leads and this can present a severe shockhazard.

Alternately, the voltage input box 125 may be plugged into jack 130 andthe test probes attached to the desired conductor.

For making the actual measurements, all that an operator is required todo is turn on the instrument 1 using the on/off switch 10, and then turnthe harmonic selector switch 16 to the desired harmonic. Or for voltageharmonic measurement, switch 126 and switch 131 must be properly set.Normally, the selector switch will initially be turned to thefundamental harmonic, whereby the display scale 14 should read 100% ifthere is sufficient current in the conductor being measured. Theoperator then would turn the selector switch to each other desiredharmonic and could record the harmonic amplitude measurements indicatedby the display scale 14. Subsequent, the operator would interpret therecorded data to determine the sources of problems that have beenencountered with particular conductors.

An exemplary data record sheet, including exemplary data, is shown inTable 1.

In reference to Table 1, the auto-gain feature of the instrument 1 wasused to determine/record the amplitude of harmonic distortion in theconductor while a suspect harmonic source, such as an SCR drive, wasturned on and off. In this manner, the auto-gain feature is particularlyuseful in locating equipment that is causing (or is the source of)harmonic distortion. From the data in Table 1, the operator would beable to trace motor overheating and excessive bearing wear to the fifthharmonic component in the motor current when the SCR drive is operatedat high power. The harmonic current causes the motor rotor to "cog" andhas the effect of hammering on the bearings. The extra current alsoincreases the operating temperature of the motor.

Also, the operator would note the concentration of harmonic current inthe capacitor. Since capacitor impedance decreases with frequency, thepresence of harmonics causes a large increase in capacitor current,resulting in heat dissipation. When the SCR drive is at idle, thedecrease is manageable, but with the SCR drive operating at high power,the capacitor current is near the limit for both the capacitor and thefuse. This could explain a capacitor fuse blowing which was observed.With the SCR drive at high power, enough harmonic distortion exists inthe line to affect computer circuits.

On the basis of the data shown in Table 1, the operator will be able torecommend a desired course of action. In this case, a course of actionwould be recommended which would improve the overall power factor andreduce the harmonic interference. For example, a tuned fifth harmonicfilter or trap, sized to improve the power factor to the desired value,could be connected to the line at the SCR drive. This should reduce theharmonic currents at the small capacitors. If the problems with highcapacitor currents continue, as determined by a recheck with theinstrument 1, replacing these capacitors with a trap is anotherpossibility.

Harmonic distortion measurements obtained using the instrument 1 couldobviously be used for many other purposes. For example, detection of thesecond harmonic of electrical energy in a conductor can be used toindicate DC current components. Also, the harmonic levels in each leg ofa three-phase system could be measured separately to determine if thephases are equally loaded.

Although there has been described what is at present considered to bethe preferred embodiment of the present invention, it will be understoodthat the invention can be embodied in other specific forms withoutdeparting from spirit or essential characteristics thereof. For example,the modified signal which is being provided to display circuit 62 couldalso (or alternatively) be provided to a computerized energy managementsystem which would automatically control the power in the conductor tobe within a desired range. Similarly, the modified signal could also beprovided to an appropriate alarm means, such as an audio alarm, a visualalarm, etc., which would be activated (for example) whenever a measuredharmonic exceeded a predetermined maximum percentage of the fundamental.

The desired embodiment is, therefore, to be considered in all aspects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than the foregoing description.

                                      TABLE 1                                     __________________________________________________________________________    PLANT X Y Z Inc.  DATE today PAGE 1   OF 1                                    LOCATION Big City, USA                                                        GENERAL DESCRIPTION of plant, problem, etc. Since installation of             SCR adjustable speed drives on blower motors, computers have been             malfunctioning. Capacitor fuses are blowing and other motors                  throughout the plant are overheating. Motor bearings are showing              abnormal wear.                                                                __________________________________________________________________________    SYSTEM NAMEPLATE VOLTAGE volts 480                                                                   RATED LOAD kva 1500                                    POWER FACTOR from utility bell 75%                                                                   LOAD CURRENT amps NA                                   POWER FACTOR measured  MEASURING INSTRUMENT                                   MEASURING POINT (diagram or description)                                                             30 hp pump motor with 7.5 KVAR                                                power factor correction capacitor.                                            A 100 KVA adjustable speed drive                                              has been added to the line and                                                its effect is to be measured.                          __________________________________________________________________________                      OVER                                                        __________________________________________________________________________    TEST NUMBER→                                                                        1a  1b 1c  2a  2b  2c                                            MEASURING POINT→                                                                    A   B  C   A   B   C                                             __________________________________________________________________________                 STATUS + = ON, - = OFF                                           EQUIPMENT = = = =                                                                          = = = =                                                                              =  =                                                                              = = = = = = = =                                                                              = =                                                                              = =                                 other equipment                                                                            +   +  +   +   +   +                                             30 hp pump motor                                                                           +   +  +   +   +   +                                             variable drive                                                                             +   +  +   -   -   -                                             POWER LEVEL→                                                                        70% 70%                                                                              70% 0   0   0                                             CURRENT amps→                                                                       26  24 32  22  23  9                                             VOLTAGE volts→                                                                      465 465                                                                              465 470 470 470                                           HARMONIC                                                                      2→    0   0  0   0   0   0                                             3→    5   0  10  0   0   0                                             HARMONIC % 5→                                                                       30  20 85  10  0   25                                            7→    5   0  20  5   0   10                                            9→    5   0  10  0   0   0                                             11→   10  5  25  0   0   0                                             13→   0   0  0   0   0   0                                             15→   5   0  10  0   0   0                                             17→   5   0  10  0   0   0                                             19→   0   0  0   0   0   0                                             PHOTO CODE→  C-70%       C-0%                                          MEASUREMENTS TAKEN BY M. Z. L., R. J.                                                                     COMPANY Myron Zucker, Inc.                        __________________________________________________________________________

We claim:
 1. Apparatus for locating and measuring harmonic distortion ina conductor, comprising:first means detachably connectable to aconductor for providing an input signal indicative of electrical energyin said conductor; second means connected to said first means andreceiving said input signal therefrom, said second means providing amodified signal indicative of the strength of a single, predeterminedharmonic of said input signal; third means connected to said secondmeans for selectively varying the single, predetermined harmonic whichis indicated by said modified signal; and said modified signal indicatesvoltage harmonics.
 2. Apparatus according to claim 1, wherein:saidapparatus further comrises a fourth means connected to said third meansand receiving said modified signal therefrom, said fourth meansproviding a display of said modified signal.
 3. Apparatus according toclaim 2, wherein:said apparatus further comprises a fifth meansinterconnected between said first and second means for automaticallycontrolling a gain of said input signal so that the said apparatus doesnot have to be recalibrated prior to each use, and so that said inputsignal remains essentially constant despite variations of the electricalenergy in said conductor.
 4. Apparatus according to claim 3,wherein:said apparatus further comprises a sixth means connected to eachof said first, second, third, fourth and fifth means for supplying powerthereto.
 5. Apparatus according to claim 1, wherein:said first meanscomprises a voltage input box including a voltage divider network toprovide a proper operating voltage.
 6. Apparatus according to claim 1,wherein:said second means comprises a filter; and said modified signalindicates the strength of the single, predetermined harmonic relative tothe strength of a fundamental frequency component of said input signal.7. Apparatus according to claim 1, wherein:said second means comprises amultiple-order programmable, switch capacitor, band pass filter; andsaid modified signal indicates the strength of the single, predeterminedharmonic relative to the strength of a fundamental frequency componentof said input signal.
 8. Apparatus according to claim 1, wherein:saidthird means comprises a frequency synthesizer.
 9. Apparatus according toclaim 8, wherein:said frequency synthesizer includes a harmonic selectorswitch adapted to be manually set by an operator to different harmonics,a source clock, and a phase lock loop connected between the source clockand the harmonic selector switch.
 10. Apparatus according to claim 9,wherein:said frequency synthesizer further comprises a programmablelogic array connected between said selector switch and said phase lockloop.
 11. Apparatus according to claim 2, wherein:said fourth meanscomprises a multi-step light bar and a plurality of LEDs associated withthe light bar.
 12. Apparatus according to claim 4, wherein:said sixthmeans comprises a rechargeable battery, a recharger circuit connected tothe battery, said recharger circuit being selectively connectable to anexternal power source and an indicator circuit connected to the batteryfor indicating when said battery is running low on power.
 13. Apparatusaccording to claim 12, wherein:said indicator circuit comprises a firstLED functioning as a voltage reference, and a second LED for indicatinglow battery power.
 14. Apparatus according to claim 13, wherein:saidsecond means includes a switch which directs said input signal to theproper part of an input signal conditioner such that said apparatus maymeasure voltage or current harmonics.